Internet access is restricted at some libraries. Photograph: Jeff Blackler/Rex Features

Comment is free, but in some places it is in chains; dictatorial regimes have a habit of blocking particular posts, as in the case of China. And then there is Hexham public library.

Try to access these and other Comment is free musings from the pleasant market town in Northumberland and you will get a message showing a red circle, as in No Cycling or No Dog Mess, and a message saying: "Stop. You cannot access this site. The site you requested is blocked under the following categories: Blogs. Wiki."

Strange. Hexham has its own local causes of passion – the doings of the huge Egger chipboard plant or maybe some of the saucier gigs at the Queen's Hall arts centre. But it isn't ruled by a China-style politbureau at county hall in Morpeth. And Northumberland's proud role of disseminating knowledge goes back to the Lindisfarne gospels and the venerable Bede.

So is Comment is free really banned? Yes it is, says the county council, and what's more that applies to all local authority public access computers from Berwick-upon-Tweed to the Newcastle and Gateshead municipal borders. Beyond these, a different regime holds sway, and all the passions and occasional wackiness, as well as the tightly argued debate on this site, are available freely.

Anything to do with the internet needs exceptional verification, and the county-wide nature of the censorship comes to you only on the word of the county council. That isn't meant to be disparaging, but it is clear from discussing the issue with county hall that exactly what is available and what isn't is not always clear even to those in charge, and so is almost certain to be inconsistent.

The frustrated Hexhamite who got in touch with the Guardian reels off evidence of this. No Comment is free, but he can get our Northerner and Dave Hill's London blog. No access to naughty Guido Fawkes, but Will Straw's Left Foot Forward blog slips through. WordPress sites appear to be banned in toto, which means that the poor chap can't email off an entry to a local cycling event.

To begin with, Northumberland responded thus: "We do use secure filters on PCs that are used by staff as well as those available to members of the public in our libraries." In conversation, however, we looked at Comment is free together and it became obvious that the site was fully available in-house to staff.

The council then said: "We have checked this out and while we can't say what specific sites might be blocked, access is filtered based on certain types of content and certain terms, and this might exclude access to some forums, bulletin boards or similar sites such as blogs. We can access Comment is free from PCs within the council so we would need to know which public access computer is being referred to check out this individual case."

So we zeroed in on Hexham, indeed on computer number 10 in the town library, but just as quickly zeroed out again, to embrace all public access computers. Because the final statement from Morpeth repeated the bit about the principles of access-filtering and then said: "You are right that Comment is free is not accessible [meaning on council computers used by the public] and this is because it is a forum."

There was also a ray of hope. Although the current policy, including a complete ban on Facebook, Twitter and streaming sites such as YouTube, follows a corporate decision endorsed by the council's library services audit, there is unease. Last word from Northumberland: "We do know that access to knowledge through technology is important to our customers and are reviewing this as part of our overall review of library services."

Which is good, because official guidance from the Museums and Libraries Association, the nearest thing to national best practice on library internet access, says of blocking and filtering: "Libraries should make this known to users and provide the opportunity for them to challenge particular instances of blocking or request the adjustment of blocking criteria. And they should recognise that such techniques are imprecise and aim to minimise restrictions and avoid inadvertent blocking of legitimate resources."

The MLA also provides case studies which show, for example, how Suffolk requires users to read and agree with the council's "acceptable internet use" policy, and accepts that "filtering can never be 100% foolproof".

And it is only fair to say that Northumberland gets a pat on the back in a different part of the censorship field. When a reader complained about the county's libraries stocking graphic novels and Japanese manga material, and about the type of young men reading them in groups, the council arranged a meeting, explained its policy of encouraging access and use and even held a subsequent book event about the medium, publicising the collection.

Maybe Comment is free will get the same in due course. But in the meantime, it would be interesting to use the scope of this site to get a national picture of blocking and filtering on public library computers. The briefest Google session shows frustrations over banning, particularly when social networks are being used to help local Save Our Library campaigns from the cuts.

Can you try yours? And let us know what you are and are not supposed to be able to access? And what you can and cannot in practice?

Sign up for the Guardian Today

Our editors' picks for the day's top news and commentary delivered to your inbox each morning.